Woocommerce 'Pay' button for failed subscription renewal orders gives 502 error (in customer login)

Hi there,
Since updating to Enfold 4.0.5, when customers login to their account on our website and try to pay for a ‘failed’ subscription renewal order, the ‘pay’ button leads to a 502 error. We have deactivated all plugins one at a time, and also contacted our host, WPEngine, who says it is a ‘segmentation fault’ most likely caused by the theme (if we have ruled out other plugins, as we have). Note they ‘pay’ button works fine for other pending orders, just not failed subscription renewals.
We also have a secondary problem (that I mention because it may be related) where failed subscription renewals trigger a ‘New subscription renewal’ email to admin, where no email should be sent for failed renewals. Seems like too much of a coincidence that both are related to subscription renewals.
Are these known problems with the latest Enfold update?
Kind regards,
David